I've opened a session (with $200 starting balance), and put some test cash transactions through. The cash total after my transactions is $250. I'd like to 'withdraw' the extra $50 to deposit at the bank

When I click 'Take Money Out', then enter $50, I get an error:

Please check that the field 'Transfer Account' is set on the company.

After a lot of Googling, there doesn't seem to be any info about this error at all (Google only returns 2 results).

Does anyone know why Odoo won't let me withdraw from the cashbox? The feature is working fine on my Odoo v8 install, so I'm completely lost.